


Bloody Hell

by Vexatious



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Biting, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Explicit Language, Explicit Sexual Content, Fellcest - Freeform, M/M, Marking, Possessive Behavior, Power Play, Rough Sex, Secret Relationship, Underfell Papyrus, Underfell Sans, Undertail, Violence
Language: English
Status: Completed
Published: 2017-11-26
Updated: 2017-11-26
Packaged: 2019-02-07 00:52:08
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,366
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12829797
Author URL: https://archiveofourown.org/users/Vexatious/pseuds/Vexatious
Summary: What do you do when you live in a universe where love is perceived as a fatal weakness? You lie about it, of course! Not that the deception doesn't have its own rewards...





	Bloody Hell

**Author's Note:**

> Based on: [18+ artwork](https://vexy-sins.tumblr.com/post/165695909318/supermuuh-heya-guys-now-it-is-your-turn-to-be) (This artist no longer draws Undertail)  
> Check out my Tumblr: [vex-bittys](http://vex-bittys.tumblr.com)

“i don’t give a fuck. i’m the older brother!”

On any given night, the denizens of Snowdin could take a stroll down the main promenade and listen to the foul-mouthed, over-the-top, wake the dead arguments of the skeleton brothers, Sans and Papyrus. Often times, the same nosy citizen would make several round trips under the thin guise of running errands just to catch the entire fight. Sibling rivalry gone bad sure beat watching MTT reruns. 

“AND I PAY THE BILLS, YOU WORTHLESS LITTLE SHIT!”

Tonight’s bout actually rattled the shutters of the skeleton brothers’ house. After weeks of arguments over a sock, things had finally boiled over, much to the delight of Snowdin’s general populace. Glass shattered, and the passersby gave up all pretense of doing anything other than eavesdropping. They speculated in loud whispers and excitedly awaited the next development. If only they could see inside the house. 

_Good thing those idiots outside couldn’t see into their house_ , thought Sans. He lazily nudged another empty liquor bottle onto the floor with his sneaker, shattering it.

“STOP THROWING THINGS OR I’LL KICK YOUR LAZY ASS, SANS!” bellowed Papyrus. More quietly, he added: “Hurry up and take your clothes off. I don’t want to keep this charade going all night.”

“eh, i’d like to see you try, dickhead!” Sans shouted, hurrying up the stairs to his brother, shedding articles of clothing as he went. When he crested the stairs, he got a nice surprise- his brother Papyrus, naked and spread out on his bed. The taller skeleton’s bones were marred with nicks and scars, but he looked gorgeous to Sans, whose magic was already starting to coalesce. 

“why are we even doing this, Boss?” whined Sans as he enthusiastically mounted the bed to stroke his brother’s lightly glowing bones. Papyrus slammed a few heavy bone attacks into the wall, causing loud thudding sounds for their outdoor audience. Irritated that Papyrus had decided to keep up the pretend fight rather than answer him, Sans leaned down and curled his tongue around his brother’s pubic symphysis. That got Papyrus’ attention.

“Hnnn… Sans!” Papyrus gasped his brother’s name as his own magic formed into a deep crimson cock, a larger and darker version of the one Sans had conjured. “You know we can’t let them know about us!” Papyrus hissed as Sans’ tongue moved up the underside of his throbbing length, clenching the sheets with both hands.

“IF YOU WEREN’T MY BROTHER, YOU’D BE DEAD WHERE YOU STAND!” Papyrus knew that soon he’d be far too distracted to think of convincing lines. Sans didn’t even care. He knew in his soul that love was seen as a weakness in Underfell. He knew that his brother’s high status would put him at risk if others knew, but he also knew that he had to hear those three little words, even just once, from Papyrus’ own mouth.

Dutiful to their improvised script, Sans used blue magic to bang a bookshelf into the wall.  _THUD!_ He didn’t feel like shouting insults with his eager brother’s unclothed body beneath him. Papyrus stared ravenously as Sans pulled himself up onto his body, using one hand to slowly caress his sensitive spine while the other hand brushed his cheek. Sans leaned down and clacked their mouths together. Papyrus opened his mouth, tongue snaking out to intensify the kiss, but Sans pulled back.

“just say it, Papyrus. you know they can’t hear us.” Using his own tongue he began to lap at Papyrus’ neck, letting his sharp teeth graze the vertebrae. 

“I won’t risk it, Sans,” growled a frustrated Papyrus, grabbing the stocky skeleton monster by the arm and flipping him so that now Papyrus was the one on top. He grabbed Sans’ cheeks in a bruising grip and forced his tongue into his older brother’s mouth. Sans moaned softly, rubbing their tongues together as Papyrus caught his hands in an iron single-handed grip and held them tightly above his head.

Papyrus raked sharp phalanges down Sans’ ribcage, making the smaller skeleton cry out in what the listeners might mistake for pain. In reality, Papyrus had his brother gasping for unneeded breaths while the tall skeleton roughly handled his sensitive bones. Leaning in close, Papyrus bit deeply into Sans’ neck, marrow oozing out around his sharp teeth. Sans could feel Papyrus’ substantial girth pressing at his tight entrance, but he wasn’t about to give in.

Teleporting out from under Papyrus, Sans landed firmly in the top position again, this time with his sternum flush with Papyrus’ spine. Bracing his hands on Papyrus’s hips, Sans simultaneously bit the back of his brother’s neck and shoved his cock into his brother’s tight hole. 

“SANS!” Papyrus screamed, a mixture of surprise and pleasure in his voice. His eyelights quickly formed into hearts as his tongue lolled, dripping crimson saliva and Sans’ blood onto the bed.

“tell. me. you. love. me.” Sans snarled, thrusting into his younger brother after each word and never releasing Papyrus’ neck from his savage jaws. Marrow welled around his sharp teeth, and he swirled it with his tongue.

Papyrus bucked his hips, catching Sans off guard enough to toss him to the floor with a crash. The back of the tall skeleton’s hand collided with Sans’ face as he fell.

“my eye!” shrieked Sans as his lithe Royal Guard brother pounced on him and pinned him to the floor, facedown. Sans rolled, bringing his own fist up to smash into Papyrus’ face once, twice, three times. Papyrus countered by catching the smaller skeleton’s fist and lifting him off of the ground by it. He slammed Sans into the wall, once again rutting his cock against Sans’ narrow little hole.

Inch by inch he entered Sans, and by the time he’d hilted himself, Sans’ angry snarls had become pleading whimpers. Releasing his brother’s arm, Papyrus pushed Sans against the wall and began fucking him hard, pounding into him so that his back slammed against the wall with each thrust. Sans wrapped his arms around Papyrus’ neck,  moaning lewdly and begging for more, harder, more. He’d almost forgotten his request from earlier, but Papyrus hadn’t.

Phalanges wrapped firmly around Sans’ cherry red cock, Papyrus began to pump up and down in time with the punishing pace of his own thrusts. 

“p-papy…. too fast… pl-please.. i’m… i’m… ahhh…AAAHHH!”

They came in unison, bright cherry cum seeping through Papyrus’ fingers as his own dark red seed filled his brother’s conjured magic. They both panted with mouths open. Tucking Sans against his chest, Papyrus lowered his voice to a harsh whisper, right into Sans’ ear canal.

“I love you, Sans.”

Sans clutched at him, still coming down from the amazing orgasm and the euphoria of the tall skeleton’s words.

“i love you too, papyrus.”

He sure could use a drink though, and from the looks of Papyrus, the tall skeleton wouldn’t say no to a shot of fire whiskey either.

“grillby’s?” he asked.

“Grillby’s.” Papyrus agreed as they scrambled to find their clothes. As they headed out the door, Papyrus quickly ran a glove across his mouth, wiping away the blood and drool, evidence of their rushed lovemaking. He quickly inspected Sans and gave him the same treatment before they entered the bar.

Papyrus ordered their drinks, and Sans lit a cigarette like the world’s biggest after sex cliche. The skeleton brothers were quite a sight to behold. Three out of four sockets were darkened and swollen, and both of their mouths were smeared with blood. Sans’ cheeks had the beginnings of dark bruises, and Papyrus could even see a bleeding bite mark low on his brother’s neck. Even Papyrus’ leather gloves bore telltale splotches of dark red.

Out on the street, wide-eyed citizens peered through the windows of the bar, trying to catch a peek at the aftermath of the battle royale they’d all been pretending not to listen to outside the skeletons’ home. “They were really going at it,” one patron gossiped to another, making Sans snort.

“They must really hate each other,” another voice commented.

Sans and Papyrus exchanged surreptitious side glances.

“I hate you, Sans,” sneered Papyrus with a barely perceptible wink.

“hate you too, bro.”


End file.
